Abstract: Currently, it is is difficult to obtain the expensive rate of expansive soil simplely and rapidly. Generally, the expensive rate can only be obtained through indoor test. It is shown that the internal structure will be changed with water swelling by previous experiments about the electrical characteristics of expansive soil in laboratory. The change of internal structure can lead to the change of resistivity. Resistivity, expensive rate and other related performance experiments are performed by using Hefei expansive soil. The resistivity index is used to predict the water swelling characteristics of expansive soil. It can be found that the expansive rate increases with the increase of initial resistivity and decreases with the increase of the overlying load. In addition, the vertical resistivity exhibits a linear increase with real-time expansion rate until the soil resistance rate reaches pore fluid resistivity. The previous experimental studies of our research group about resistivity characteristics of expansive soil are used to analyze and contrast. It can be found that expansion characteristics of expansive soil have a good fit with resistivity properties. Hence, the resistivity can be used to predict expansion rate. As the corresponding expensive rate is a dimensionless index, through the normalization of cohesive soil resistivity and regardless of the influence of the porosity, the relationship between dimensionless integrated resistivity index Er and the expensive rate is developed. The conclusions can be used for the expansion rate prediction of expansive soil.

Key words: expansive soil, expansive rate, electrical resistivity, laboratory test